This invention relates to a developer cartridge detachably mounted to an image forming portion. This invention also relates to an image forming unit and an image forming apparatus using the developer cartridge.
A conventional developer cartridge of a type which is detachably mounted to an image forming apparatus has a developer storing portion that stores developer. A developer outlet opening having an elongated shape is formed on the bottom of the developer storing portion. The developer cartridge further includes a shutter supported at both ends in the longitudinal direction thereof so as to slide to open and close the developer outlet opening. A seal member composed of resilient member is attached to the shutter. When the shutter closes the developer outlet opening, the seal member covers the developer outlet opening and is pressed against the peripheral portion of the developer outlet opening. Such a developer cartridge is disclosed by, for example, Japanese Laid-open Patent Publication No. 2006-243446 (paragraphs 0024-0040, FIGS. 1-5).
In the above described developer cartridge, there is a possibility that the developer may leak outside the developer storing portion even when the shutter closes the developer outlet opening.